There are on the market a large number of medicament delivery devices such as injectors having a number of different features and/or functions to be able to deliver a certain dose quantity to the user in a safe, reliable and reasonably simple and intuitive manner.
One drawback that many delivery devices suffer from is that the number of components tends to increase dramatically when the number of functions and features are increasing, where the functions could be any or several of mixing, priming, penetration, medicament delivery, withdrawal and covering of the injection needle.
The added complexity regarding the number of components and their interaction in order to perform the desired functions may make it difficult to actually have a reliable functionality without undue precision and tolerance demands and or expensive choice of material, which of course adds to the cost of the medicament delivery device.
Some attempts have been made in order to try to keep the number of components on reasonable levels and yet have a reliable device with a number of functions. The document WO 2005046770 discloses a medicament delivery device arranged with a dose setting drum that is threaded onto a threaded section of a plunger rod for setting a dose. Dose quantity indications are arranged on the dose setting drum. However, in order to obtain an injection operation after a set dose, a number of components are required, for instance for preventing the dose setting drum from rotating relative the plunger rod.